Method of making structural materials



Nov. 2, 1943. T, sENDZlMlR 2,333,343

METHOD OF MAKING STRUCTURAL MATERIALS Original Filed April 22, 1937 2Sheets-Sheet 1 INVENTOR.

BY W M Nov; 2, 1943.

T. SENDZIMIR METHOD OF MAKING STRUCTURAL MATERIALS 2 Sheets-Sheet 2Original Filed April 22, 1937 llllllllllllllllllllllllllll IIIII'IIIIIII'IIIIIIIIII"Il/ FIG.3

02% 0M E I N mu m N vea m M 2 WM METHGB F MAKHNG @TBUCTURAL MATHEWSTafleusz Senflzimlr, ltdirlsllletown, Ohio, assigns? to Armzen Comoany,Middletown, ()liio, cor= aeration of Delaware Claims. (f/l. 29-188) isnot so limited and is applicable to other ma terials, such as cellulose,paper, veneer, Bakelite, asbestos and other sheet-like materials.

An object of the invention is to provide a structural materiel of almostuniversal application, of light specific weight, and having a highmechanical resistance in all directions. Another object to provideamaterial through which heat and sound penetrate only with difilculty,and which resists corrosion. A further object is to provide a materialthat can stand a very considerable deformation before breaking.

These and other objects of my invention which will be pointed outhereinafter or will be appareat to one skilled in the art upon readingthese specifications, I accomplish by that certain construction andarrangement of parts, and in that process of which I shall now describecertain exemplary embodiments. Reference is made to the drawingswherein:

Figure l is a sectional view showing an assembly having cell closingelements.

Figure 2 shows another form of structural element.

figure 3 shows yet another form of structural element in perspective.

Figure 4 shows the same structure in section.

Figure 5 shows a curved section formed in one of my elements.

Figure 6 is a diagrammatic illustration in a step of a process ofmanufacturing my elements.

Figure 7 is a digrammatic sectional view of the immediate product of thestep illustrated in Figure 6.

Figure 8 is a sectional view of a mould member.

The multicellular structural elements which arethe subject of thisapplication are assemblies of a plurality of preformed pieces ofsheetlike material, dividing the space between the two outer surfaces ofthe element into a relatively great number of individually enclosedcells. The axes of such cells are usually parallel to the greaterdimension of the plate and, in cases where resistance to corrosion foralmost unlimited periods of time is of first importance, they aresubdivided lengthwise each into a number of shorter cells, by insertingor fixing blocking pieces at intervals, as will be more fully described.

In my sections, blocks of metal may be inserted and solidly welded atspaced intervals, into the individual cells, blocking each cell orsubdividing it into a number of shorter cells, each hermetisally sealedfrom the others, as shown at lL-"lt, cl-tt in Figure 4. Such blocks maybe solid blocks of metal, or stamping s, or may consist of anothermaterial which is simply pressed between the individual channels andadequate- 1y closes or seals each section of a cellule. Such sealingblocks also reenforce the whole section mechanically and wherever thisis imp-ortant, should be placed so that they always lie on the samecross section of the plate, and so that their stiffening effect iscontinuous, over the whole section.

The resistance to bending, for a given weight per unit of surface.depends upon the thickness of the element and on the proportion of metalsituated at or near the outside surfaces. From this point of View thepresent invention offers an almost ideal solution, Whenever the maximumresistance to bending is desired, the outside plates can be made thick.The inside structure can, in such cases, be made just strong enough tohold the outside portions rigidly and to prevent them from collapsing.For other prevalent combinations of forces, f. i. twisting, crushing,another distribution of metal across its thickness may be preferable,and the method lends itself always to the ready securing of the optimumconditions. It may be desirable, in some cases, to make the outsidecellules smaller, and therefore stronger, than the inside ones. This hasbeen shown in Figure l, where the outside cellules are smaller than theinside cellules.

The cellular sections may or may not be symmetrical. The section shownin Figure 1 is symmetrical. such disposition may lead to savings inweight. Take first a section like this subject to a bending movementalone. The outer fibres are in such case subject to tension andcompression of equal magnitude and therefore should, theoreticallyspeaking. be equally dimensioned. In case of the fibres subject totension, however, a great safety factor is usually required than inthose subject to compression, chiefly because possible cracks,non-metallic inclusions, etc. would weaken fibre subject to tension muchmore than fibre subject to compression. The necessity of providing forthis extra safety factor on tensioned fibres or cellules of the sectiononly,

longitudinal section through such plate.

can be taken advantage of, with this invention, by making such sectionsnon-symmetrical.

Depending on the purpose for which my structural element is to be used,its construction may be varied. Where heat insulation is the chiefobjective, it is better to use many small cellules of very fine gauge,right across the sections; and it would be wasteful to increase thedepth of the middle ones, especially as the thickness of the plate isfrequently limited.

Another example is where resistance to penetration of a foreign body,like a projectile, is the foremost objective. This construction is idealfor such purpose, if properly designed, and offers a resistance manytimes greater than a solid armour plate of the best alloy-steel. Forhigh muzzle velocities, inner sheets of extremely light gauge arepreferred, as their inertia is small and they yield before being punchedthrough. In fact, the action of such plate may be likened to the way athin wire net fencing behaves, under the force of a bull; it yields butdoes not break. With a suitable distribution of gauges and be welded onone side, when assembling the plate (depending upon the assemblypressure to make the joint sufficiently air-tight), or they may besoldered or brazed or suitable non-metallic filling media or cements maybe applied to make the joint absolutely airtight, or other preferablyplastic materials may be employed to fill up the pores. One such way isto use a filler which,

' when heated, vulcanizes or polymerizes and joins sizes of theindividual cellules which, in this case,

may preferably have a wavy and not a rectilinear contour but in eithercase a foreign body trying to penetrate into the section will bedeforming not only the cellules which are in its way, but

a relatively large adjacent area of cellules. Consequently the kineticor other energy of. such foreign body or projectile is quickly used upand its speed of penetration brought to zero before it has penetratedthe element.

The factor of utmost importance is the light gauge of the individualsections which with projectiles of high velocity, do not become pierceddirectly and individually, as the projectile moves through the element,but begin to bend or yield or elongate and involve a large mass ofcellules in such deformation. This consumes a great deal of energy andtherefore has a superior braking effect on such foreign body.

The great value of mystructural elements, as far as resistance tocorrosion is concerned, lies in the fact that, behind an outside platewhich either is corrosion-resisting or can easily be made so (as bypainting or metal spraying), lies a web of little cellules each of whichis hermetically sealed in itself. There can be no corrosion where thereis no access of air and moisture. however, the outside surface bedamaged, for instance the outside wall of a house, should someone drilla hole in it, corrosion can only affect one cell, namely, the one thathas been opened up; and not until this one has been destroyed cancorrosion proceed any further. This means that there would be many yearsbefore any serious damage could be done to a building, if such hole isleft unprotected. If the hole is noticed, it can simply be patched up bycement or any suitable means and corrosion immediately stops.

It has been mentioned above that the blocks used for hermeticallysealing the sections of a cellule, reenforce it mechanically. If'suchblocks are suitably disposed, in the neighbouring cellules, so as to lieall in one cross section of the plate, then the whole element isreenforced across this section. The blocks can be made use of still foranother purpose: Figure 1 represents; 13, etc., are end sealing blocksand 8|, 82, 83, etc., are inside sealing blocks. They may be made ofmetal, wood, cement, Bakelite or any suitable material. If metallic,they may be solid blocks of metal, or stampings, and they may eitherShould,.

with both the sheets of the section and the material of the sealingblock, like ebonite or some of the synthetic resin compounds. Anordinary cement, in suitable combinations may also be used. I

In any case, such a zdne as is indicated at A in Figure l, which hasthus been reenforced, can be used for the purpose of obtaining amechanically sound joint between one plate and another, as, in thiszone, the plate presents practically a solid section and holes may bedrilled in it, bolts put through or any suitable means of connectionapplied. Forces transmittedlocally by such bolts or other. means ofconnection are distributed uniformly to all of the plates and cellulesforming parts of the element. The sides of the plates may be similarlyreenforced, for this purpose, just the same as the ends.

If vulcanization, or another operation requiring a high temperature, isrequired to join the sealing blocks with the sheets, it is preferable todo it under conditions of elevated pressure,

so that, upon cooling, there will be no partial vacuum within the platewhich might impair its mechanical resistance.

Figures 2, 3 and 4 represent multicellular elements built on the sameprinciple, with the corrugated sheet sections extending parallel to thesurface of the elements. To make the drawings clearer, plates with acomparatively small number of cellules are shown; but many more may beused in practice, depending upon the purpose for which the plates are tobe used. It will be noticed that this form of plate construction has adecided advantage when equally strong bending moments, both in thedirection of the length of the elements as well as at right angles toit, are tobe taken up.

Figure 2 shows such an element still further simplified and consistingonly of two external plates and one corrugated sheet in between.

For the most economical use of the sheet metal, elements such as thoseshown in Figures 1 to 4 are preferably not made of sheets all of thesame gauge, On the contrary, it is preferable to use heavier gauges forthe outer sheets 4, 3, 2 and 2', 3, 4' and lighter for the inner sheetsi, I and I.

By suitably disposing the sheets, this method may also be used forproducing curved or bent plates, as shown in Figure 5 at B.

Ordinary manufacturing methods for such elements will be clear to theskilled worker in the art and need not be described. There are, however,two developments which produce results unobtainable by ordinary methods:

Strip which is cold rolled or drawn in rolls of very small diameters andpossesses a high tensile strength but is not too brittle may beemployed. Such strip, whether of low or medium carbon content steel,can, for certain purposes, be used without annealing; and its structureresembles one of a steel rope. With the use of such material, it wasfound that a large number of spot welds of very small diameter give verygood reaasases suits, as such welds are close enough to one another toinsure tight joints and the portions annealed through the welds aresmall enough not to impair the very high mechanical'value of theelement. Each individual weld does not need to be strong, as they holdonly by their great number.

Another development is an economical method of producing elements of thetype of Figures and 6. This is done in conjunction with metal coatingmachines for strips according to applicants copending application No.31,699, filed July 16, 1935, now Patent No. 2,110,893, dated March 15,1938. The exit side of such apparatus is represented in Figure 6. 38 isan airtight cooling compartment of an annealing furnacethrough whichpass, while being partially cooled, a number of superimposed strips 9!.The rurnace has a reducing atmosphere, The strips have undergone apreliminary treatment before they enter the furnace, in that certainportions of them which are notto receive any metallic coating have beengiven a preventive coat of heatresisting. non-metallic substance such aslime,

graphite, magnesia or other, alone or in com-' bination, or containing abinding substance like sodium silicate, clay, etc.

While still within the cooling chamber 98, the

. strips are separated by being led over pulleys 93 and individuallyenter a bath of a coating metal, such as cadmium, zinc, bronze or othermolten metal, that portion of the bath surface where the strips enterinto the, bath being protected from contact with the outside air by asuitably shaped exit portion of the cooling chamber, the edges of whichare submerged into the metal coating bath.

The strips now travel acertain distance in the bath individually, bothsurfaces of each strip being in contact with the coating bath. Thustheir surfaces obtain a metallic coating, continuous, excepting for theplaces which have on them the preventive coating above referred to.

The strips now go round the roll 34 while submerged in the coating bathwhere they are brought together, and move vertically through exit rolls5 to cooling and shearing means,

It is evident that a partial'cross section of such composite strip aftercooling will appear as shown in Figure 7. Outside are the two thickerstrips tilt and I02 which, in this process, have incidentally obtained acorrosion-proof outside coating. Inside are the thin sheets m3, I04,I95, Hi6 brazed to each other, or to the outside trips but only atplaces indicated at it].

Such brazed elements can now easily be expanded to form a multicellularplate of the general type of Figure 3 by gripping one end of a shearedlength and introducing a liquid or gas under pressure at the other.

Such treatment, for preventing certain parts of a strip from obtaining ametallic coating, can of course, also be used for other purposes, suchas for sheets coated on one side only, etc.

In certain instances, I prefer statically to expanel the elements whiledelimiting their outside contour, as by first placing them in a mould158, Figure 8. This prevents buckling and allows enough pressure to beapplied to iron out any wrinkles that may be produced on the outsidesurface of the element, especially when the outside sheets are notsufiiciently heavy in proportion to the inside sheets. The expansion ofthe element in thickness necessitates a certain amount of drawing on thepart of the inner of their cross section. Unless the outside sheets aresufliciently heavy to insure this, the whole element may become narrowerwith resulting wrinkles on the outside sheets. rected and the wrinklesironed out during the flnal stage of expansion within a mould.

Such mould can also be used advantageously in order to producemulticellular plates which are not flat but are curved or varying inthickness etc. The elements have been found, to be very plastic duringsuch expansion and can be made to 1111 different shaped moulds, withincertain limits, of course.

Modifications may be made in my invention without departing from thespirit of it. Having thus described my invention, what I claim as newand desire to secure by Letters Patent is:

l. A process for the production of multi-cellular plates consisting inapplying a coating-preventive layer on the surfaces of sheets where theywill not be brazed together and where cellules are to be formed, thenapplying a metallic coating to each sheet individually, withdrawing themfrom the metallic coating bath and cooling them jointly whereby to bracethem together along uninterrupted spaced llnes and finally expanding theplate, to produce cellules.

2. A process for the production of multl-cellular plates consisting inapplying a coating-preventive layer on the surfaces of sheets where theyare not to be brazed together and where cellules are to be formed, thenapplying a metallic coating to each sheet individually by passing saidsheets through a bath of molten coating metal, withdrawing them from thebath, superposing them and cooling them in superposition, whereby tobrace them together along two opposed sides of the plate and in thoseareas to which the coating preventive layer was not applied, and finallyexpanding the plate so formed to produce cellules.

3. A process for the production of multi-cellular plates comprisingapplying a coating-preventive layer to sheet surfaces to prevent brazingwhere eellules are to be formed, then applying a metallic coating tosheets by passing them individually through a bath of molten coatingmetal, superposing the sheets before the coating thereon has hardened,and cooling them in superposition, whereby to braze them together inthose areas not affected by the coating-preventive layer, and finallyexpanding the plate so layer to sheet surfaces to prevent brazing wherecellules are to be formed, then applying a. metallic coating to sheetsby passing them individually through a bath of molten coating metal,superposing the sheets before the coating thereon has hardened, andcooling them in superposition, whereby to braze them together in thoseareas not afi'ected by the coating-preventive layer, and finallyexpanding the plate so formed to produce cellules, the said platecomprising external sheets and at least one internal sheet, the saidexternal sheets being of heavier gauge than the remainder, and effectingthe expansion by subjecting the plate to internal fluid pressureinsuficient substantially to stretch and deform the external sheets,whereby these sheets remain in subsantlally smooth and uncorrugatedcondition, but sumcient to stretch and deform This can be cor-,theremainder, whereby to produce a cellular product.

tive layer,- and finally expanding the plate so formed to producecellules, the said plate comprising external sheets and at least oneinternal sheet, and the expanding operation comprising the steps oflocating the plate in a mold and subjecting it to internal fluidpressure so as to cause the entire structure when in expanded form tofill substantially the entire mold cavity, whereby to produce astructure which is cellular 10 within and has relatively smoothsurfaces.

TADEUSZ SENDZIMIR.

